.box{
    width:700px;
    margin:50px auto;
    display: flex;
}
.leftbox{
    height:300px;
    width:300px;
    position: relative;
}
.leftbox img{
    height:300px;
    width:300px;
}
.mark{
    height:100px;
    width:100px;
    background-color: red;
    opacity: 0.5;
    position: absolute;
    left:0;
    top:0;
    display: none;
    /* padding:30px;
    border:10px solid red;
    box-sizing: border-box; */
}
.rightbox{
    height:400px;
    width:400px;
    overflow: hidden;
    position: relative;
    display: none;
}
.rightbox img{
    /* height:1200px;
    width:1200px; */
    position: absolute;
    left:0;
    top:0;
}